A Universal Mobile Telecommunication System (UMTS) is a broadband, packet based system for the transmission of text, digitized voice, video and multi-media. In a UMTS based network, a mobile wireless device, referred to as user equipment (UE), can be in an “idle mode” or in a “connected mode.” In the idle mode, the UE can request a radio resource control (RRC) connection from a wireless network to send user data to the wireless network, to initiate a voice connection and to respond to a page for receiving a voice connection or data from the wireless network. The UE can reduce battery consumption in the idle mode or connected mode by minimizing when circuits are active and by also minimizing which circuits are used while monitoring the network for connection initiation messages to which to respond. In the idle mode or the connected mode, the UE can use additional circuitry when required to improve radio reception performance. Thus a UE can trade off power consumption for improved wireless performance as required by selectively enabling and disabling power consuming circuitry in the UE.
When connected to the wireless network, the UE can be in one of four states. Each connected state can consume a different amount of power from a battery in the UE.
CELL-DCH: A dedicated channel is allocated to the UE in the uplink and downlink directions to exchange data. As the UE can be actively transmitting and receiving in the CELL-DCH state, this state can consume the most power.
CELL-FACH: No dedicated channel is allocated to the UE; instead, common channels are used to exchange a small amount of bursty data. While the UE can be limited in transmission and reception capabilities in this state, the UE can still be considered “active” continuously, albeit consuming power at a lower level than in the CELL-DCH state.
CELL-PCH: The UE can use Discontinuous Reception (DRX) to monitor broadcast messages and pages through a Paging Indicator Channel (PICH) and no uplink activity can be possible. With no uplink transmission and limited downlink reception, the UE can consume less power in this state than in the CELL-DCH and CELL-FACH states. Power consumption can also be minimized by using a minimal set of circuitry in the UE when monitoring for broadcast messages and pages.
URA-PCH: similar to CELL-PCH, except a UTRAN Registration Area (URA) UPDATE procedure is triggered through URA reselection.
When not communicating with the wireless network, the UE can conserve battery power by “sleeping” and periodically “waking” during a series of successive DRX cycles to monitor the page indicator channel for broadcast messages and pages that can indicate an incoming call or data. The UE can also receive updated wireless network system information during the “wake” portion of a DRX cycle. When “asleep”, the UE can disable most active circuitry to minimize power consumption. When “awake”, the UE can use limited active circuitry to also minimize power consumption and can selectively add active circuitry as required based on measured operating conditions to maintain or improve performance. During an “awake” portion of a DRX cycle, the UE can receive signals typically through one antenna connected to one receive signal chain, even when the UE can include multiple antennas and multiple receive signal chains, in order to limit current drain from the UE's battery. When located in an area of the wireless network with weak signal coverage, the UE, however, can be unable to correctly receive pages or can declare an “out of service” condition based on measurements of weak signals received through the sole operating antenna and receive signal chain. To improve signal coverage for the UE to detect pages from and to maintain connections with the wireless network, selective use of more than one antenna and receive signal chain in the UE can be implemented to balance minimizing battery power drain and increased performance. This selective use can be referred to as selective receive diversity.
Therefore, a need exists for a method and apparatus for selectively enabling and disabling one or more of a plurality of receivers during certain operating states in a mobile wireless device in communication with a wireless network.